Personally, I do not believe in a Judgement Day. I don't personally believe our decisions are tallied up at the end of our lives and weighed on a scale. That allows me to see Calvin's, Aquinas' and others "compatabilism" as the, well. To be be direct, it paints them into a corner which precludes a sentient, benevolent God. In accepting that free will is in fact provided by our Creator, and yet God, who is omnipotent, predetermined all of it. And so, why would God make any creatures suffer in ignorance (the world that did not have his Word), struggle in pain to hopefully make correct decisions which leads either to nirvana or burning Hell? Because he wanted to. And an onmipotent God wants for nothing.
And if you set aside the reasons for doing this to us (because, we can't know the mind of God, etc etc), then how can it be benevolent to give people the free will to allow themselves to burn in hell, while at the same time predestining them to do so?
It is a self contradicting mess, I'm afraid. One that neither the Bible nor the philosophers (and I tackled Hume, Kant, Spinoza etc) can answer to satisfaction.
I think you have to utilize the evidence of observation. Clearly, evil actions are a choice by those not insane (i.e., incapable of fully understanding social norms). We know it, because we make those choices. We see others do so. Ergo, free will exists.
But also we know that we are largely the product of what we have observed. Moral relativism may not be absolute, but we learn what our own particular society views as evil, and make choices within that structure. We know that a human being raised in the wild will have a different set of standards, one circling around survival. A more brutal world, and one that has made up the vast majority of humankind's time on Earth. Was it evil to kill your brother and take his woman or his food, before concepts of evil existed? According to Plato's forms, sure it was. I trend towards thinking that evil is a social word, and society is what separates us from the animals. But invented and measured by us.